1. Field of the Invention:
The present invention relates to a film inking unit for a rotary printing press.
2. Description of the Prior Art:
A generic film inking unit is known from German Patent No. 29 42 734 which discloses a device for the return of ink and ink-water mixtures consisting of a cage-like container equipped with a plurality of roller elements which are in contact with each other, are mounted non-stationarily so as to be rotatable and which have circular cross-sections. On one side of the container, at least one of said roller elements can be driven by the ink fountain roller and on the other side of the container at least a second roller element can be driven by a subsequent fast-running roller. Such a device serves the purpose of continuously returning the ink-water mixture from the inking unit into the ink fountain. However, it cannot be excluded that, via the film roller, the roller elements carry ink from the ink fountain roller into the inking unit. Providing a plurality of roller elements which loosely rotate in the housing is rather elaborate and moreover causes additional noise. This device is neither designed nor suitable for minimizing the amount of ink forwarded from the ink fountain to the inking unit.
French Patent No. 1 401 718 specifies a short inking unit in which, via three intermediate rollers, an ink fountain roller transfers the ink directly onto an applicator roller for a plate cylinder. Thus, this inking unit relates to another species. FIG. 5 of this patent, however, shows an additional ink roller which is arranged beside the rollers transferring the printing ink and cooperates with a doctor blade. As specified on page 3, left column, fourth paragraph of this patent, the additional ink roller makes it possible to combine an ink knife and a doctor blade such that together they form an ink reservoir.
In order to reduce the thickness of an ink film in a film inking unit, German Patent No. 34 01 886 assigns to an ink roller of the ink roller train, a blade device which is engaged at the cylindrical surface of said ink roller, as seen in direction of rotation of said ink roller, after the ink transfer to the next ink roller. [See, for example, FIG. 9 of the patent.] In general, vibrator rollers have been used to minimize the ink transfer into the inking unit, as described in European Patent No. 0 036 103 and in other publications, the vibrator rollers being engageable only temporarily at the ink fountain roller and disengageable therefrom, respectively. At high machine speeds such ink vibrators are subjected to considerable strain. In particular, in the case of zones of very low ink consumption, the minimum ink transfer which can be attained is still too great, even when using such known vibrator rollers.
All of the above-mentioned patent and/or publications are hereby expressly incorporated by reference with the same effect as if their entire contents were set forth in full herein.